In most current Code Division Multiple Access (CDMA) systems, such as systems conforming to the Wideband CDMA (W-CDMA) specifications promulgated by the 3rd-Generation Partnership Project (3GPP), transmit power control is accomplished using two simultaneously operating control loops: an inner and outer power control loop. In a typical inner-loop power control procedure, a signal quality measure for a received signal, such as signal-to-interference ratio (SIR), is compared to a target level, to generate transmit power control (TPC) commands for instructing the transmitter to either increase or decrease its transmit power. The outer control loop, which generally operates more slowly than the inner loop, adjusts the targeted signal quality measure so that a desired quality of service (QoS) is achieved. For instance, an SIR target employed by the inner loop may be adjusted by the outer loop to maintain a designed block error rate (BLER) or frame error rate (FER). The general operation of inner- and outer-loop power control is well known, and is described, for instance, in U.S. Patent Application Publication No. 2005/0143112 by Jonsson, the entire contents of which are incorporated herein by reference.
In a dynamic radio environment, the target SIR must be continuously adjusted to maintain the target BLER under changing signal propagation conditions. Further, the target SIR must be adjusted to accommodate changes of the BLER target. Rapid convergence of the power control loop to the target BLER is highly desired, since excessive transmit power causes interference to other communications, while transmissions at below the optimal level result in excessive error rates at the target receiver. However, conventional control loops designed for quick response often exhibit large jumps in transmit power, thus wasting power and/or missing the BLER target. These control loops may be stabilized, but the price for the stability measures used in existing power control loops is generally a slow convergence to the SIR target and excessive transmit power.